type signature lock

[cuzfrog]

What it is

A new module gate named signature-gate. It locks the captured signature of named types declared in a module's MODULE.md. A locked declaration can still have its body edited; only the captured head (parameter list, return type, generics, class extends/implements, interface body, or type-alias RHS) must remain unchanged.

Module descriptor syntax

signature-lock:
  - my-type.ts$MyFunction
  - sub/foo.ts$Bar

Each entry is file$Name. The $ separates the file path from the symbol name. The file path is resolved relative to the directory containing the MODULE.md. Multi-level subdirectories are not supported in v1.

What counts as a signature change

A signature change is any edit that alters the captured head of a locked name in the target file. For a function, adding a parameter or changing the return type breaks the lock. Changing only the body is allowed.

Behavior

• Cascade order in run-gates.ts: readonly -> sealed -> signature -> export -> module-interface-import.
• The lock applies regardless of which file is editing the locked name.
• Bodies remain editable for locked declarations.
• Dangling entries (a lock that points at a name or file that no longer exists) produce a warning at index time and do not block writes.

v1 limitations

• Signatures are extracted via regex, not AST. Multi-line parameter lists with inline comments inside parens may produce false positives.
• Interfaces are locked in their entirety; the interface body is part of the captured signature.
• Class inner methods are not individually lockable; only the class header is captured.
• Only TypeScript/JavaScript ships a complete checker. Rust, Java, Go, Kotlin, Scala stubs return empty maps, so signature-lock entries for those languages are silently ignored.